More than 100,000 people are expected to be in Windsor — a small medieval town made up of narrow streets — to watch the procession.

“It’s a hell of a job to secure,” Dai Davies, former head of royal protection, told CBS News. “It has narrow streets, cobbled in parts. How do you secure several miles of very small township and parts which are open and green?”

Another factor bumping up the bill is that more than 2,000 members of the public are expected to attend Windsor Castle for celebrations on the big day.

Critics, such as a group called Republic, say the government should disclose exactly how much taxpayers will spend on Saturday’s affair.

“A royal wedding is a private, personal event, dressed up as a national occasion,” reads their newly launched petition that has so far garnered over 30,000 signatures. “Taxpayers should not be funding a private wedding, no matter who is getting married.”